how many intergers between 299 and 501 are divisible by both 2 and 5

Question

1.) 12

2.) 20

3.) 21

4.) 100

Answer 1

The are 21 integers divisible by both 2 and 5.

They are 300, 310, 320, . . . . . , 480, 490, 500.

These are the integers which are divisible by 10 -- which is divisible by 2 and by 5.

Answer 2

integers divisible by 5 end in 0 or 5

integers divisible by 2 must be even

So, 300, 310, 320, 330, ..., 500